The present invention relates to a process for the preparation of fatty acid or hydroxy fatty acid esters of isopropylidene derivatives of a polyglycerol from C.sub.1 -C.sub.4 -alkyl esters of C.sub.6 -C.sub.22 -fatty acids or mono- or polyhydroxy fatty acids, by reaction in alkaline medium with one or more hydroxyl-containing isopropylidene derivatives of at least one polyglycerol under specific conditions.
It is already known to prepare fatty acid esters, for example tetraesters of polyglycerols, by heating diglycerol for several days with a large excess of fatty acids, for example lauric, palmitic, stearic and oleic acid, in the form of brown, solid or oily compounds (cf. C.A. 41,2392 (1947)). As a result of the long heating, however, only heavily contaminated products can be obtained in very poor yields.
Therefore, an attempt has been made to obtain the corresponding compounds from isopropylidenediglycerol and stearyl-chloride in chloroform. However, the necessary amount of work involved is considerable, since the mixture solidifies after the reaction to yield a paste which after 36 hours has to be taken up in benzene. After the aqueous solution has been separated off and the organic phase washed with water, excess stearic acid must be removed by extraction with 10% strength sodium bicarbonate solution. The organic phase must then be dried over sodium sulfate and the solvent must be distilled off. The resulting residue must be recrystallized twice or several times with alcohols. A further disadvantageous aspect of this process is the fact that hydrochlorides are formed in molar ratios, which either have to be processed further or will represent undesirable impurities in the final product.